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Foods fortified with vitamin D have proved to be effective in avoiding vitamin D deficiency among Danish and Pakistani women during winter, according to a study from the National Food Institute.

Vitamin D is important e.g. for bone health, because the vitamin helps the body absorb calcium from the foods we eat. During the summer, most Danes get the required amount of vitamin D from sunlight, as the vitamin is synthesized when the sunlight's UVB rays hit the skin.

However, approximately one in 10 Danes develop vitamin D deficiency during the winter, when the sun's UVB rays are not strong enough for vitamin D to form in the skin. A PhD study from the National Food Institute, Technical University of Denmark, has shown that it is possible to avoid deficiency by eating foods fortified with vitamin D in the winter.

How the study was structured

In the study, 143 women of Danish and Pakistani origin consumed vitamin D fortified cheese, yogurt, crispbread and eggs for three months, which they received from the National Food Institute. Half of the participants received vitamin D fortified products, while the other half received placebo products. It was a double-blind study. As such, neither the participants nor the researchers knew who received what.

At the start of the study, the women’s blood concentration of vitamin D was on average about 50 nanomoles per liter (nmol/L). A vitamin D concentration below 30 nmol/L is considered harmful to bone health. At the start of the study, the blood concentration of vitamin D was below 30 nmol/L in 9% of the Danish and 24% of the Pakistani women.

After consumption of the vitamin D fortified products for three months, none of the Danish women were vitamin D deficient, whereas this was the case in 23% of the women, who had consumed the placebo products. Among the Pakistani women, the figures were 3% and 34% respectively.

Overall, Ida Marie Grønborg's study shows that intake of vitamin D fortified foods can alleviate the vitamin D deficiency that occurs in Denmark during the winter.

Not many vitamin D fortified foods in Denmark

Under Danish legislation, food producers are able to add vitamin D to a number of foods, as long as they label the foods as being fortified. However, unlike in countries such as Sweden, Finland, Norway, Germany and Holland, there are only very few vitamin D fortified foods on the Danish market.

A copy of Ida Marie Grønborg’s PhD thesis is available from the National Food Institute. The thesis will be uploaded to DTU Orbit, when the other articles contained within the thesis have been published. Email food@food.dtu.dk if you want to be notified when the thesis is publically available.

The PhD study was part of ODIN FOOD, which is part of a larger European research project: ODIN. The aim of the ODIN project is to produce knowledge, which can prevent vitamin D deficiency among EU citizens through food. The National Food Institute is lead on ODIN FOOD, which has a focus on vitamin D deficiency in adult women.